In the testing and production of hydrocarbon wells, specialized couplings are provided which incorporate seals to prevent leakage between the coupling components. One such coupling is known as a union and comprises a coarse male thread on one of the components which cooperates with coarse female threads on a collar to provide a quick connect/disconnect coupling.
A more specialized quick connect/disconnect coupling is known as a hammer union which comprises four components: a thread end having coarse male threads on the exterior, a seal on the inside of the thread end, a nut end having a smooth nose abutting the seal and a hammer nut having coarse female threads on the interior and ears on the exterior which may be struck with a hammer to cinch up the coupling. Because hammer unions have the capability of being quickly connected and disconnected, they are widely used in temporary installations or in equipment which is expected to be disassembled periodically.
Hammer unions have not been redesigned in many decades. The seal in a conventional hammer union is a large annular rubber seal that is basically rectangular in cross section. One of the coupling components provides a groove or rabbit receiving the annular rubber seal which is compressed between the coupling components when they are cinched up, thereby providing a seal. The rubber component is exposed to gases, fluids and abrasives flowing in the interior flow passage of the coupling. This conventional seal has withstood the test of time and has basically been unchanged for at least fifty years.
One of the situations where hammer unions are widely used is in equipment to test gas wells after they are initially completed or after recompletion from one zone to another. Typically, regulatory agencies require that gas wells be tested to provide a measure of gas deliverability and pressure using chokes of several different size. To enforce these regulations, regulatory agencies often will not allow a well to be produced into a sales line before testing. Test equipment typically comprises a trailer having an inlet end for connection to the well head, a separator for separating gas and liquid, an orifice meter for measuring the gas from the well and an outlet for connection to a flow line leading to a flare.
Many gas wells, particularly those completed at depth, do not produce commercial quantities of natural gas until they are fraced. It is a tribute to the research of major oil companies and major oil field service companies that modern frac techniques convert large numbers of conventionally completed uneconomic wells into economic ones. A typical current frac job injects a liquid or gel containing 500,000 or so pounds of sand or other proppant under pressure into a well to create, propagate and prop open a vertical fracture extending many hundreds of feet away from a well bore to provide a high permeability flow path from a relatively low permeability formation to the well bore.
One of the facts of life of fracturing a well with a large quantity of sand or other proppant is that not all of the proppant stays in the hydrocarbon zone when the well is produced. When production starts, some of the proppant returns to the well bore and is produced at the surface.
Hammer unions are also widely used on drilling rigs to make mud line connections, to make connections in cementing operations and to pump various liquids into a well bore during completion operations.
Disclosures of some interest relative to this invention are U.S. Pat. Nos. 2,726,104; 3,140,107; 3,848,905; 4,930,791 and U.S. Patent Publication H945.